Trigo Identities
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Any idea/guide into solving it?
I suck in it...zzz always cannot prove >_>. -
when in doubt, always resolve into just sine and cosine.
Work halfways from both sides
Join it up
Almost 80+% of the time can solve by this brute force method -
have u had ur identities memorised by heart? while they do provide certain identities, its essential to memorise all ur identities so u can recognize when and where to change the identities and more importantly, when NOT to change the identity when doing so would be irrelevant
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Sometimes changing them to tan and sec could be helpful too.
Some questions involve simple algebraic identities a²-b²=(a-b)(a+b)
Some may involve multiple angle, which we all hate most probably
But eagle is right. Work halfways, or work from RHS if LHS seems impossible.
To proof is to find a mathematical "pathway" from one to another and that's all you need. -
Just to addon, if u r stuck from working for example from RHS. Don't just give up. Start working from the LHS writing your ans in a rough paper and stop at the point when u obtain the same term as from your RHS. Then, play cheat by reversing the process.Originally posted by ^tamago^:Sometimes changing them to tan and sec could be helpful too.
Some questions involve simple algebraic identities a²-b²=(a-b)(a+b)
Some may involve multiple angle, which we all hate most probably
But eagle is right. Work halfways, or work from RHS if LHS seems impossible.
To proof is to find a mathematical "pathway" from one to another and that's all you need.
It is easy to simplify and cancel out common term but is difficult to add term. -
Oh ya, I forgot to mention
Usually start from the side that looks more complicated -
trigo identity actually got only 2 (up to sec 3 lvl)
which is "tan x = sin x/cos x" , and "sin² x + cos² x = 1"
other ones like "tan² x + 1 = sec² x" are derived from "sin² x + cos² x = 1"